Abstract
The infrared chemiluminescence (``arrested relaxation'') approach has been applied to the measurement of initial vibrational, rotational, and translational energies (V′, R′, and T′) in the products of the exothermic reactions F + H2 → HF + H and F + D2 → DF + D. Detailed rate constants k(V′, R′, T′) are reported as contour plots. The total detailed rate constants into specified vibrational quantum states (summed over the rotational levels of each v′ level) are: (i) for F + H2, k(v′ = 1) = 0.31, [k(v′ = 2) = 1.00], k(v′ = 3) = 0.47; (ii) for F+D2, k(v′ = 1) = 0.28, k(v′ = 2) = 0.65, [k(v′ = 3) = 1.00], k(v′ = 4) = 0.71. Both reactions convert the total available energy quite efficiently into internal excitation of the new molecule. The mean fractions entering vibration plus rotation are: (i) for F+H2, f̄V′ + f̄R′ (= 0.66 ± 0.08) = 0.74; (ii) for F + D2, f̄V′ + f̄R′ ( = 0.66 + 0.08) = 0.74. The fractional conversion of available energy into vibration is comparable to that for the Cl+HI reaction (Part IV of this series) and markedly greater than that for H+Cl2 (Part V). It seems probable that the energy release is predominantly ``repulsive'' in all these reactions, but is more efficiently channeled into product vibration if the attacking atom is heavy (Cl+HI, F+H2). As in the case of other isotopic pairs of reactions (Parts IV and V of this series) there is a parallelism in k(V′) though not in k(v′) between the members of the pair. The present reactions exhibit only a small increase in product rotational excitation with decreasing vibrational excitation (— Δ R̂′ / Δ V′ more closely resembles that for the H+Cl2 reaction than that for the reaction Cl+HI). It follows that the translational energy of the products is markedly greater for successively lower v′ states.
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@article{Polanyi_1972, title={Energy Distribution Among Reaction Products. VI. F+H2, D2}, volume={57}, ISSN={1089-7690}, url={http://dx.doi.org/10.1063/1.1678438}, DOI={10.1063/1.1678438}, number={4}, journal={The Journal of Chemical Physics}, publisher={AIP Publishing}, author={Polanyi, J. C. and Woodall, K. B.}, year={1972}, month=aug, pages={1574–1586} }